Until recently, laser devices for commercial and experimental applications had been capable of producing beams of coherent optical radiation only at discrete wavelengths. Eye-protective goggles for use with such discrete-wavelength laser devices were correspondingly sensitive to discrete wavelengths. Thus, a researcher working with a number of different laser devices for producing beams of coherent radiation at a number of different wavelengths generally needed a corresponding number of different sets of safety goggles, i.e., a different set of goggles for each laser wavelength being produced.
Recently, variable-wavelength dye lasers (i.e., laser devices using a complex organic "dye" as the lasing element) have become commercially available for producing beams of coherent optical radiation at selectable wavelengths in a broad spectral band. Dye lasers are marketed by, e.g., Coherent Inc. of Palo Alto, Calif. and Spectra-Physics Inc. of Mountain View, Calif. However, until the present invention, there had been no tunable eye-protective gear available for use with variable-wavelength dye lasers.
Researchers working with variable-wavelength dye lasers have perceived a need for tunable eye-protective goggles capable of attenuating a selected wavelength while passing a broad band of optical radiation. Tunable birefringent filters have been used in astronomical applications for selectively passing or blocking particular wavelengths of radiation from distant sources such as solar flares. However, until the present invention, practitioners in the art relating to eye-protective gear did not recognize that tunable birefringent filter devices could be adapted for use in adjustably attenuating the intensity of radiation from variable-wavelength lasers. An article entitled "Tunable Birefringent Filters" by A. M. Title and W. J. Rosenberg, published in Optical Engineering, Vol. 20, No. 6, (Nov.-Dec. 1981), pp. 815-821, provides a technical description of tunable birefringent filters.